As a mobile machine, e.g., truck, travels, the tires on the machine generate heat due to the friction of the tires on the surface the machine is traveling on. The heat generated is a function of the load being carried by the mobile machine and the speed that the machine travels. Tire wear can be attributed to the generation of heat for long periods of time. In addition, excessive amounts of heat generation can lead to early tire failure.
Currently, ton-miles-per-hour, a standard indicator in the tire industry of the heat generated in a tire during use, is determined by calculating the average tire load and the average speed of a mobile machine, and multiplying the two averages to get an "average" ton-miles-per-hour figure. For example, in U.S. Pat. No. 5,327,347, Hagenbuch discloses a system in which ton-miles-per-hour is calculated when there is a change in weight of a vehicle, e.g., after a load or a dump. The speed of the vehicle is determined by dividing the distance traveled by the time of travel.
However, calculating "average" ton-miles-per-hour does not give a good indication of the wear on a tire during operation. Ton-miles-per-hour is directly correlated to the heat generated by a tire that carries a specified load at a specified ground speed which, in turn, is directly correlated to tire wear. For accurate monitoring of tire wear, the load and ground speed must be monitored in real time. For example, an operator driving at excessive speeds while hauling a full load generates a ton-miles-per-hour factor higher than an operator driving at a slower speed while carrying the same load. The higher ton-miles-per-hour figure may exceed the rating of the tire, resulting in excessive wear on the tires. Calculating an average ton-miles-per-hour does not account for excessive tire wear during intervals of high speed driving.
In addition, calculating an average ton-miles-per-hour figure does not take into account uneven distribution of loads on a mobile machine, which would cause the ton-miles-per-hour to vary significantly from tire to tire. For example, a truck hauling a load may have more weight from the load over the rear tires than the front tires. This would result in ton-miles-per-hour figures that are higher for the rear tires than for the front tires. Therefore, the rear tires would experience more tire wear due to heat and load than the front tires. The averaging methods described above would not account for this uneven tire wear.
The present invention is directed to overcoming one or more of the problems as set forth above.